A liquid-liquid extraction is one of significant methods of chemical separation, and performs purifications or separations of each component by using different distribution rates between two solvents immiscible to each other or between two solvents partly miscible. An extraction tower is one of the key devices of extraction process and the main advantage thereof is adapted to implement a large scale continuous production. Within the extraction tower, under an action of gravity, a dispersed phase in manner of liquid droplet group counter-current-wise contacts with a continuous phase due to a density difference, so as to implement a mass transfer. As shown in FIG. 1, a typical extraction tower in the related art is provided.
For the extraction tower, especially for the execration tower without external power, a packing is very important, because the packing can prevent the continuous phase from axially back-mixing and facilitates crushing, gathering and re-dispersing of the dispersed phase by providing a surface area to improve the effects of the mass transfer. Thus, current studies and researches of the extraction tower are mostly focused on the structure improvements of the packing which can facilitate a smooth flowing of the continuous phase and the gathering and dispersing of the dispersed phase.
However, in the conditions of a small density difference between the two phases and a high viscosity of the continuous phase, the axial back-mixing of the extraction tower in the related art is very serious, especially the axial back-mixing of the continuous phase, so that a production capacity and a separation efficiency of the extraction tower are greatly reduced.